The objective of the research is to develop new research projects on cellular and molecular changes that occur during aging. Dr. Church will analyze the synthesis of collagen in cells from skin, cornea and lens; he will also analyze the activities of the enzymes involved in the modification of the primary translation product which determine the structure of the completed molecule. Dr. Hoffee will analyze the properties of deoxyribose-5-aldolase in rat liver. The enzyme may play a key role in the regulation of the cell cycle, and exhibits different properties in old animals. The mechanisms involved in the change will be analyzed by studying the purified protein. Finally Drs. Lombardi and Ove will study carcinogenesis. The induction of hepatic tumors by chemical carcinogens will be studied as a function of age in control animals and in animals subjected to nutritional deprivation. The promotional phase of neoplasia will be studied in similar animals, and also, by studying the growth of transplantable hepatomas. As a first step to elucidate possible mechanisms, the activity of DNA repair enzymes will be studied. The research should lead to an understanding of age-related changes in connective tissues, enzyme acitvity, and tumor development.